Compare No Man of Woman Born, which is a prophecy that acts as an If/Then Statement. Like that trope, the No Escape Clause is usually something ludicrously unlikely (of course, we all know how statistics play out in stories). Playing with the language of the escape clause is common; sometimes the words are twisted around to use puns or less obvious meanings but this is so old that taking it literally has become more common.

Alas, forbidding someone to do something because such abstinence is needed to break the curse tends to be Forbidden Fruit.

In Bloody Cross, all half-bloods are cursed to die by the age of 18, but the curse can be removed by either drinking the blood of a pure demon or finding a powerful enough God's inheritence to remove it.

One XXXenophile story had a genie and his mortal lover, who (before the story began) had gained her freedom when her oppressor changed her name, thus qualifying her for three additional standard wishes. She wants to set the genie free, but can only do so by making a wish he truly cannot grant. She wishes for him to make love to her until he's exhausted, which he does. Then she wishes for him... to do it again. Which he's too tired to do, thus freeing him. (He promises to make good on it once he's rested up, though.) Another story featured the warrior Blue Opal who, in a homage to Red Sonja, was prohibited from indulging sexually unless defeated in combat first. A traveler tries to take her mind off things by teaching her a strategy game... and upon winning the first time, accidentally breaks the prohibition. Turns out the game was called, in the traveler's native language, "Combat"...

During one Incredible Hulk story arc, the Hulk reverted to a mindless brute and was sent to "the Crossroads" by Doctor Strange. From this nexus he could go to almost any world (except straight back to Earth), with the caveat that, if he were truly unhappy in a given world, he would be sent back to the Crossroads to choose again.

Disney's Beauty and the Beast had the enchantress give the stipulation that if the Beast could learn to love someone selflessly, and have his love returned by the time the petals fall off a magical rose, the spell would be broken. Possibly to Teach Him A Lesson but her motives aren't revealed.

Disney's adaptation of Hercules involved a deal made between Hercules and Hades where Hercules would give his powers up for 24 hours in exchange for the safety of his Love Interest Megara. After a fight between Hercules and the Cyclops, a pillar was knocked onto Meg, killing her. As a result, Hercules' powers were restored.

In Shrek, Princess Fiona is cursed from a young age to transform into an ogre at sunset and return to her human form at sunrise. It can only be undone by True Love's Kiss—but when this kiss comes from the titular male ogre, she finds herself permanently stuck in her night form, for better or for worse.

Fun trivia? In the original storyboards, the "night" form was her NATURAL form! She was actually under an enchantment to be beautiful during the day. This makes sense, in light of her father being a frog.

Shrek Forever After further plays with it by noting that Rumpelstiltskin is obligated to provide an escape clause in his contracts, and he's had to resort to alternate forms of trickery to hide it. In Shrek's case, the words are scattered willy-nilly about the page and it requires origami to put it together.

In The Swan Princess, the curse that turns Odette into a swan and back ostensibly can only be broken by Rothbart himself if she marries him. It's later revealed that if her sweetheart Derek makes a vow of love to her that he then proves to the world, that will be enough to break it.

The spell Queen Grimhilde of Snow White A The Seven Dwarfs places on the apple. It stipulates that one who suffers from the sleeping death can be cured only by love's first kiss. Grimhilde dismisses the loophole since Snow White will be taken for dead and buried alive. Grimhilde obviously didn't read a lot of fairy tales as a child.

In George MacDonald's Little Daylight, a princess is cursed to be nocturnal and have her beauty wax and wane with the moon. When the moon is full, she's very beautiful and looks as young as she is; as it wanes, she gradually loses her beauty and seems to age. The condition of the curse ending is that a prince kiss her without knowing it. (It's broken when a prince meets her or sees her when the moon is full, and then later meets her when the moon is new and (platonically) kisses the "old woman" he sees without knowing it's her.)

In Neil Gaiman's Stardust, a fairy woman is bound into service until "the moon loses her daughter, if it happens in a week when two Mondays come together". The condition is met by the moon "losing" her daughter (the star) to love, in the same week that Mr. Monday gets married.

In George MacDonald's The Light Princess, a witch curses a baby princess with her Baptismal water (it's a very Christian book) to "lose her gravity"—which means that she's tossed about by the slightest breeze, and that she cannot take anything seriously. The only time she is unaffected is in the water, so the kingdom's finest scientists reason that if she can be made to cry, the spell will be undone.

These are apparently mandatory on the Discworld: in Sourcery, a dying wizard tries to cheat Death by transferring his essence into his sourcerer (not a typo) son's staff. Death reminds him that, because only he is inescapable, there must be some loophole in the prophecy. The loophole is that the wizard would truly die when his son voluntarily threw away his staff. Which he did when he realized he just wanted to be an eight year old boy, not the most powerful wizard on the Disc.

The wizard had originally tried "till hell froze over," but Death stopped him because he was "not allowed to enlighten [him] on the temperature of the next world."

In the Second Chronicles of Thomas Covenant, one of the subplots involves a sorcerer who uses pure gold as his power source, but must deliberately put a flaw in each spell. For example, he created a magical prison for the destructive Sandgorgons, the flaw being that if a particular Sandgorgon's name is spoken aloud, it is released until it kills the speaker. He wants Covenant's white gold ring, because being an alloy, it is "flawed" already, and thus can be used to create perfect works.

In Mercedes Lackey's Tales of the Five Hundred Kingdoms series, setting and foiling these clauses is practically a science (though it would have to be, since the ambient magic in the land causes events to turn out like whichever fairy tale they most resemble).

In Dragonsbane, by Barbara Hambly, the villainess performs a curse without 'limitations' and summons a dragon which she refuses to banish. The heroine later figures out that she can't banish it, not won't, since the 'limitations' keep the curse alive and give the caster ongoing control over it..

In James Schmitz's Telzey Amberdon short story "Child of the Gods", Telzey is mentally enslaved by another psionic, with several of her most potent skills locked away. When the man is incapacitated and a monstrously powerful alien is shortly due to arrive to enslave and/or eat them, Telzey breaks free when she realizes that his command to look after his best interests—without him conscious to decide otherwise—would best be served if she had full access to all her abilities and was free of his control so she could use them most effectively.

In Jim C. HinesPrincess Series curse loopholes are explained as being about leverage and possibility; a truly unbreakable spell would require an enormous amounts of power but true love is rare enough that it's functionally the same as an unbreakable curse. Which also implies that people only hear about the notable cases—the rare ones that have been broken.

Shadow Spell by Caro King (from "Seven Sorcerers"" series) features many of them:

Azork - If he ever feels love again, his existence as leader of Cryptmonsters ends.

Simeon Dark - if somebody tells him who he is, he will remember everything and become the sorcerer again

Cleverly applied in Buffy and Angel: Angelus, described as "the most evil vampire on record," is cursed with a human soul, which comes with a human sense of morality, making him feel guilty for all the evil things he did. the clever part is that the escape clause is "if he experiences true happiness", which in the season it became a plot point is explicitly defined as "one moment when his soul is at peace". Effectively meaning that the curse would break only when it was no longer making him suffer. When Angel has his night with Buffy, the one he loves, in the second season of her show, it's enough to activate the Curse Escape Clause and before Buffy knows it, it's Angelus time.

The curse is later deliberately broken when they need to ask Angelus some things Angel doesn't know, by hiring someone to feed him into a magic Lotus Eater Machine.

It was a bit subverted (not sure if that'd be the right word for this) when Wesley tells Angel to stop using the curse as an excuse not to go after a relationship opportunity with an interested woman (who Angel met because she was bitten by a werewolf). After all, as Wes puts it, "Most of us have to settle for adequate happiness."

In the Ravenloft campaign setting for Dungeons & Dragons, if any character speaks a curse against somebody, they may attract the attention of the Dark Powers that control the setting, which will inflict the curse upon the victim. This is more likely to happen if the curse has an escape clause.

The Book of Vile Darkness gives us dying curses, which are spoken by an evil creature as it dies. There are two ways to cure them - one is ninth-level magic, and one is a condition set at the time of casting (such as "Climb the tallest mountain in the world"). These may be completed by someone acting on the cursed's behalf, as long as they do so explicitly to lift the curse (for example, if a peasant didn't know the king was cursed and climbed the tallest mountain in the world, nothing would happen - but if the king's champion did so in his lord's name, the curse would be lifted).

Inverted in New World of Darkness game Changeling: The Lost. One power changelings get is the ability to create Pledges—magically binding agreements with a range of possible effects. For instance, a person may agree to do a changeling's laundry in exchange for having a servant show up out of nowhere and work for them free of charge. While low-power pledges can be of the "do this to get that" variety, increasing power requires both parties to stipulate some kind of increasingly-bad punishment for breaking the pledge. Fortunately, they can be made for a set duration.

However, it is possible to work around the conditions of a pledge, which is why most people with a brain don't try making deals with the Gentry—they likely know every trick in the book. Similarly, the Gentry have made deals with the very nature of creation, but as a result of such phenomenal cosmic power, they're inflicted with Frailties, things that weaken them or cause them harm. The intro fiction to one book has an abducted mortal realize her captor kept visiting her at twilight, compares it to the situation in the Celtic myth above, and waits for the time to take advantage of an in-between state.

Mage: The Awakening plays it straight with conditional durations that can be set for spells by a mage with sufficient power over Fate. It allows a mage to extend the duration of a spell, in return for setting a condition under which the spell will end instantly (the easier the condition, the longer the duration). Its explicitly noted that impossible conditions (such as "When the moon falls") cannot be set. It's also subverted with the Curses of the Proximus bloodlines (families of mortals with a magical heritage). If a Proximus family attempts to exploit loopholes in their family Curse, the Curse just alters itself to become worse, while closing off the loophole.

For game balance reasons this is required for any "permanent" effect in GURPS.

In Into the Woods, the witch's spell causing the Baker's family to be barren will be lifted if the Baker and his wife can procure a few select objects. (The objects are not directly related to the curse on the Baker's family: they're actually part of the Escape Clause for a curse that the witch is suffering under, and she promises to take the spell off the Baker if he helps her out.)

In the Gilbert and Sullivan opera, Ruddigore, Baronets of Ruddigore are cursed to do an evil deed every day or die painfully. The main character outwits the curse by pointing out that not doing an evil deed is the same thing as killing himself, which is in and of itself an evil deed.

In the musical Once Upon a Mattress King Sextimus the Silent is mute until "the mouse devours the hawk".

City of Villains characters can be cursed by the Circle of Thorns with a particularly nasty curse that will cause them to undergo the same horrible end that the Circle's enemies, the descendants of the Mu, are planned to face. It's not clear exactly what the result of the curse itself would be, but the Circle were going to slowly torture and kill each Mu, then rip out and then send to a special corner of Hell their souls to be the feed of a demon named Lilitu. As there's roughly 1 billion descendants of Mu on the planet, and the player character would have that done roughly a billion times simultaneously to him or her, mystically inclined contacts tend to assume the term blast radius is apt. Destroying and trapping Lilitu prevents the curse from working.

Presented in the Quest for Glory series introduces the concept of a counter-curse that can, well, undo the original curse. The manual for the original game (Hero's Quest) stated that the more powerful the curse used, the less stringent the counter-curse would be. In other words, if a curse was overly powerful, then undoing it would be child's play, but if the curse is minor, countering it would require very specific conditions to occur. And all curses and counter-curses are in rhyming verse, which necessarily results in ambiguity. The player character naturally undoes the curse (though, strangely enough, it's not required to fulfill all the objectives of the counter-curse to win the game, resulting in the game telling you What the Hell, Hero?.) The counter curse is a follows:

Come a hero from the EastYou arrive from the eastern pass into Spielburg during the introFree the man within the beastThe Baron's son has been turned into a bear, you need to change him back to a human.Bring the child from out the bandThe Baron's daughter has been enchanted and became the leader of the bandits. She needs to have the enchantment lifted.Drive the curser from the landBaba Yaga laid the curse, she needs to be driven out of Spielburg.

Invoked with King's Quest VI where Alexander is cursed by the Beast. Alex, being a minor sorcerer, points out that every curse has a weakness to which the Beast tells him to go out and fetch a "Beauty" for him.

Lampshaded then averted in the AGD InteractiveKing's Quest games. The Big Baddid put Graham under a curse. All parts of the curse (the family in danger, Graham's heart attack, Rosella and Alexander not inheriting the throne) came true, but not in the way the Big Bad wanted!

In Fantasy Quest, you can break the curse on a man trapped as a dog by feeding him. This serves mainly as mad mockery; the dog appeared in the first game, you had no option to feed him, and now he's retconned as a man still bitter about your earlier indifference.

One Story Arc in Sluggy Freelance involves a private war between a couple ghosts. One ghost is cursed to play Solitaire over and over until he wins, which he can't do because his deck is missing one card. The 52nd card is framed behind glass, with a sign saying only to break the glass in an emergency.

In one Arthur, King of Time and Space strip, the sorceress Morgan mentions that every curse needs to have an out, "or the spell is structurally unsound and won't work".

In pages 94 through 105 of Looking for Group, Richard's imp Hctib Elttil puts a pendant on him that shrinks him to the size of a toddler, which also makes him a lot weaker. The pendant's curse can only be broken by performing a selfless act. Seeing as this is Richard, he seems to be screwed. But when the building he and a small boy are in is about to explode, Richard protects the kid with his magic, causing the curse to be broken.

Gargoyles loved this one. The original "permanent statue" spell had the Gargoyles as statues until their castle "rose above the clouds." (The magi's flowery way of saying "for all eternity".) When too-bored, too-smart, and too-rich David Xanatos moved their castle onto his skyscraper, it did just that. He wanted to see if it would work.

This only applies to human magic. Fae magic is a bit more relaxed for the user and as such, they don't usually have escape clauses... they are more commands.

Elisa uses Loophole Abuse to undo a spell that made Goliath into an obedient, unthinking slave, by ordering him to behave exactly as if he's not under the spell. Although this loophole wasn't built into the magic by its caster, the nature of this command evidently cancels it out entirely, as Goliath not only resumes behaving normally but ceases to look ensorcelled.

In the series Aladdin, Agrabbah was once attacked by a would-be conqueror while Aladdin, Jasmine and Genie were away on other business. In desperation, the Sultan donned a suit of enchanted armor that would make him "as strong as stone". The armor allowed him to defeat the conqueror, but also allowed the spirit of the armor's original wearer, an evil sultan of Agrabbah's past, to possess him, turning him evil and paranoid to the point where he tried having Jasmine executed. Aladdin realized that "as strong as stone" meant that the armor drew its magic from a stone statue of the evil sultan, and was able to break the spell and restore Jasmine's father to his old self by coercing him into destroying the statue.